improved the circle drawing code, so that either the x- or y-axis distance properly determines the circle radius
added circle and ellipse drawing modes that work like freehand drawing but the nearest circle/ellipse corresponding to the input coordinates is drawn (makes use of the conicfit package)
in type mode, text is immediately shown while typing; can use
can now toggle through four different point symbols and three different line types
added a smooth mode for freehand drawing
much faster undo for freehand drawing
info at the top now also shows the drawing mode; can click on the boxes to select the mode / color (or to toggle smooth/snap/symbol)
added option to rescale the visual information via the info argument
minor documentation updates
use on.exit() as needed to reset par() changes